Faba bean production under Norwegian growing conditions
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Faba bean production under Norwegian growing conditions
By Anne Marthe Lundby, PhD candidate, NIBIO dep. Grain and forage seed agronomy
One of the main goals for the PhD project is to improve agronomic strategies for food-grade faba bean under a cooler climate. We want to look deeper into management practices, including fertilization strategies and Rhizobium inoculation. How can management and environmental factors affect the accumulation of starches, proteins and anti-nutrients during seed development?
Field trials
Field trials are the basis of this PhD work, and we now have completed two years of field trials. Field trials have provided us with a large amount of information about plant development, chlorophyll content, flowering time, soil temperature, diseases, yield and nodulation. We also harvested pods every week during the seed development, for analysing of starches, proteins and anti-nutrients. In the field trials we have used the variety Vertigo.
Nodulation
Legumes, like faba bean, can fix atmospheric nitrogen through a symbiosis with nodule bacteria, Rhizobium leguminosarum. These bacteria are naturally occurring in the soil. Inoculating faba bean with Rhizobium is not considered necessary in Norway today, but is used in other countries as a common strategy to improve nitrogen fixation. In the field trials, we have included Rhizobium inoculation, to see if this can lead to an earlier and more uniform nodulation.
Figure 1 shows an example from the nodule scoring in 2019. We scored higher number of nodules in the upper part of the roots that had been inoculated with Rhizobium. For the lower part of the root, we did not see any difference. At the same time, we also measured the crops’ nitrogen status. In the field trials, the nitrogen balance index (NBI) was in general higher for the plants inoculated with Rhizobium. More results from field trials are needed before we can conclude on the effects of inoculation.
Experiments under controlled climate
In addition to field trials, we also carried out a greenhouse experiment in 2019 with two faba bean varieties Vertigo and Sampo. The aim was to investigate the accumulation of starches, proteins and anti-nutrients under different temperatures. In addition, we made registrations regarding different yield component.
The plants were grown under the same temperature until the beginning of flowering, and then divided into three different temperatures; 14/12, 19/12 and 24/12 °C (day/night). For each temperature, we harvested pods three times during seed development, based on the growing degree days (GDD) after start of flowering. On the last harvest date the plants in the highest temperature (24/12 °C) had reached maturity. For each harvest date we counted the number of pods and seeds, before weighing and measuring the water content. The number of pods varies along the stem, with the most mature pods being concentrated on the lower nodes.
At the highest temperature (24/12 °C) we counted less pods on the higher nodes compared to cooler temperatures. In total, the plants at 19/12 and 14/12 °C had more pods than the plants at 24/12 °C. The bar chart in figure 3 shows the number of seeds per plant for the variety Vertigo at different temperatures and GDD. We counted most seeds at 19/12 °C. The line chart represents the dry weight per seed (mg). As expected, the seeds on the lowest nodes have the highest weight, since these are the first initiated. The plants grown in the highest temperatures (24/12 °C) reached maturity, but this was not the case for the lower temperatures. In this experiment, the highest yield was achieved a 19/12 °C.
The stem continues to grow during flowering, and many floral nodes can be produced. However, the number of pods that develop will be lower than the number of flowers initiated, due to flower and/or pod abortion. Faba bean has a great ability to regulate yield potential under different temperatures. These results will provide us with a better understanding of how faba beans react to different temperatures, and will allow us to better interpret the crop failure that was experienced in the drought of 2018.
Plan for 2020
Field trial can be risky, as results are dependent on weather conditions. Drought was a problem in several trials in 2018, and in 2019 the results from one field trial had to be disregarded due to very late harvesting conditions. Field trials are challenging, but absolutely necessary in order to understand the growth and development of faba beans under Norwegian conditions. We are therefore planning three new field trials in 2020. We cross ours fingers, and hope for a good growing season. A large number of seed samples have been collected from the field trial in this WP, and the next large assignment will be to start analysing the material for starches, proteins and anti-nutrients. The results from this work will provide us with a better understanding of the accumulation of these components under our growing conditions and various management strategies.